What is the cube root of w?
(1) The 5th root of w is 64.
(2) The 15th root of w is 4.
OA D
Source: Official Guide
What is the cube root of w?
This topic has expert replies

 Moderator
 Posts: 5050
 Joined: 07 Sep 2017
 Followed by:16 members
GMAT/MBA Expert
 Jay@ManhattanReview
 GMAT Instructor
 Posts: 3007
 Joined: 22 Aug 2016
 Location: Grand Central / New York
 Thanked: 470 times
 Followed by:32 members
Timer
00:00
Your Answer
A
B
C
D
E
Global Stats
Let's take each statement one by one.BTGmoderatorDC wrote:What is the cube root of w?
(1) The 5th root of w is 64.
(2) The 15th root of w is 4.
OA D
Source: Official Guide
(1) The 5th root of w is 64.
=> w^(1/5) = 64
w = (64)^5
=> w^(1/3) = (64)^5 = [(64)^5]^(1/3) = (64)^(5/3) = A unqiue value
Sufficient.
(2) The 15th root of w is 4.
=> w^(1/15) = 4
w = (4)^(15)
=> w^(1/3) = (4)^(15) = [(4)^(15)]^(1/3) = 4^5 = A unqiue value
Sufficient.
The correct answer: D
Hope this helps!
Jay
_________________
Manhattan Review GMAT Prep
Locations: GMAT Classes in Manhattan  GMAT Tutoring New York  GRE Prep Seattle  Manhattan TOEFL  and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
GMAT/MBA Expert
 Brent@GMATPrepNow
 GMAT Instructor
 Posts: 15003
 Joined: 08 Dec 2008
 Location: Vancouver, BC
 Thanked: 5254 times
 Followed by:1265 members
 GMAT Score:770
Timer
00:00
Your Answer
A
B
C
D
E
Global Stats
Target question: What is the cube root of w?BTGmoderatorDC wrote: ↑Tue Feb 26, 2019 9:36 pmWhat is the cube root of w?
(1) The 5th root of w is 64.
(2) The 15th root of w is 4.
OA D
Source: Official Guide
Statement 1: The 5th root of w is 64.
ASIDE: If the square root of x = 7, then x = 7²
If the cube root of x = 10, then x = 10³
If the fourth root of x = 6, then x = 6⁴
etc
So, if the 5th root of w is 64, then w = 64⁵
Since we COULD determine the actual value of w, we COULD find the cube root of w
In other words, we have all of the information we need to answer the target question with certainty
Statement 1 is SUFFICIENT
Statement 2: The 15th root of w is 4
From this we can conclude that w = 4¹⁵
Since we COULD determine the actual value of w, we COULD find the cube root of w
In other words, we have all of the information we need to answer the target question with certainty
Statement 2 is SUFFICIENT
Answer: D
Cheers,
Brent
Brent Hanneson  Creator of GMATPrepNow.com
If you enjoy my solutions, I think you'll like my GMAT prep course
Watch these video reviews of my course
And check out these free resources
If you enjoy my solutions, I think you'll like my GMAT prep course
Watch these video reviews of my course
And check out these free resources